News tagged with nanocomposite

Ruthless with bacteria, harmless to human cells. New, durable antibacterial coatings of nanocomposites, developed at the Institute of Physical Chemistry of the Polish Academy of Sciences in Warsaw, will in future help to ...

Making a paper airplane in school used to mean trouble. Today it signals a promising discovery in materials science research that could help next-generation technology -like wearable energy storage devices- get off the ground. ...

(Phys.org) —Single-walled carbon nanotubes (SWCNTs) are being widely studied for their potential applications in many areas; for example, as electrode materials for energy storage, as transparent conductive films, and as ...

Researchers from North Carolina State University and the University of Texas have revealed more about graphene's mechanical properties and demonstrated a technique to improve the stretchability of graphene – developments ...

Nearly everyone is familiar with the polytetrafluoroethylene (PTFE), otherwise known as Teflon, the brand name used by the chemical company DuPont. Famous for being "non-sticky" and water repellent, PTFE is a dry lubricant ...

A new "solder" for laser welding of tissue during surgical operations has the potential to produce stronger seals and expand use of this alternative to conventional sutures and stapling in intestinal surgery, scientists are ...

Thermoelectric devices—which can either generate an electric current from a difference in temperature or use electricity to produce heating or cooling without moving parts—have been explored in the laboratory since the ...

Arthrobotrys oligospora doesn't live a charmed life; it survives on a diet of roundworm. But a discovery by a team led by Mingjun Zhang, an associate professor of biomedical engineering at the University of Tennessee, Knoxville, ...

Following last year's earthquake and tsunami at Japan's Fukushima nuclear power plants, many nuclear scientists have been focused on developing models to predict what will happen under a variety of conditions that may exist ...

Nanocomposite

A nanocomposite is as a multiphase solid material where one of the phases has one, two or three dimensions of less than 100 nanometers (nm), or structures having nano-scale repeat distances between the different phases that make up the material. In the broadest sense this definition can include porous media, colloids, gels and copolymers, but is more usually taken to mean the solid combination of a bulk matrix and nano-dimensional phase(s) differing in properties due to dissimilarities in structure and chemistry. The mechanical, electrical, thermal, optical, electrochemical, catalytic properties of the nanocomposite will differ markedly from that of the component materials. Size limits for these effects have been proposed, <5 nm for catalytic activity, <20 nm for making a hard magnetic material soft, <50 nm for refractive index changes, and <100 nm for achieving superparamagnetism, mechanical strengthening or restricting matrix dislocation movement.

Nanocomposites are found in nature, for example in the structure of the abalone shell and bone. The use of nanoparticle-rich materials long predates the understanding of the physical and chemical nature of these materials. Jose-Yacaman et al. investigated the origin of the depth of colour and the resistance to acids and bio-corrosion of Maya blue paint, attributing it to a nanoparticle mechanism. From the mid 1950s nanoscale organo-clays have been used to control flow of polymer solutions (e.g. as paint viscosifiers) or the constitution of gels (e.g. as a thickening substance in cosmetics, keeping the preparations in homogeneous form). By the 1970s polymer/clay composites were the topic of textbooks, although the term "nanocomposites" was not in common use.

In mechanical terms, nanocomposites differ from conventional composite materials due to the exceptionally high surface to volume ratio of the reinforcing phase and/or its exceptionally high aspect ratio. The reinforcing material can be made up of particles (e.g. minerals), sheets (e.g. exfoliated clay stacks) or fibres (e.g. carbon nanotubes or electrospun fibres). The area of the interface between the matrix and reinforcement phase(s) is typically an order of magnitude greater than for conventional composite materials. The matrix material properties are significantly affected in the vicinity of the reinforcement. Ajayan et al. note that with polymer nanocomposites, properties related to local chemistry, degree of thermoset cure, polymer chain mobility, polymer chain conformation, degree of polymer chain ordering or crystallinity can all vary significantly and continuously from the interface with the reinforcement into the bulk of the matrix.

This large amount of reinforcement surface area means that a relatively small amount of nanoscale reinforcement can have an observable effect on the macroscale properties of the composite. For example, adding carbon nanotubes improves the electrical and thermal conductivity. Other kinds of nanoparticulates may result in enhanced optical properties, dielectric properties, heat resistance or mechanical properties such as stiffness, strength and resistance to wear and damage. In general, the nano reinforcement is dispersed into the matrix during processing. The percentage by weight (called mass fraction) of the nanoparticulates introduced can remain very low (on the order of 0.5% to 5%) due to the low filler percolation threshold, especially for the most commonly used non-spherical, high aspect ratio fillers (e.g. nanometer-thin platelets, such as clays, or nanometer-diameter cylinders, such as carbon nanotubes).